Wakasa Oniga Castle, Castle ruins in Wakasa, Tottori Prefecture, Japan

Wakasa Oniga Castle is a ruined mountain castle on Mount Tsuruoyama in Wakasa, Tottori Prefecture. Its summit holds a roughly pentagonal central bailey with 50-meter sides, containing the 10-meter-square foundations of a tenshu, entered through a compound gate to the northwest. Two further enclosures with stone-walled gates lie down the slopes; the whole site measures about 150 by 50 meters.

Built around 1200 by Yabe Terutane, the castle stayed with the Yabe clan until 1575, when Yamanaka Yukimori seized it and then abandoned it the next year under attack by the Mōri. Toyotomi Hideyoshi gave it to Kinoshita Shigekata, who rebuilt it with stone walls; after 1600 it passed to Yamazaki Iemori. When his son moved to Bitchu in 1617, the one-castle-per-province rule ended it.

The castle's name links it to the oni, the demons of Japanese folklore, and the hilltop is called Tsuruoyama. The site is counted among the three great castles of Inaba Province, alongside Tottori and Kano castles, and in 2017 it was chosen as No. 168 of the Continued Top 100 Japanese Castles. Visitors can still trace the ridge-top enclosures of the Yabe clan's older fort and the later stone-walled baileys.

The hike to the ruins takes about 50 minutes from the Baba parking area to the mountain summit. Bring sturdy footwear and plenty of water, as the trail is steep and can be slippery in places.

The castle's central bailey is roughly pentagonal with 50-metre sides and holds the ruined foundations of a tenshu 10 metres square. The whole site measures about 150 by 50 metres, and the 1617 demolition left collapsed stone walls visible in the main enclosure.